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Lens Evaluation

A

Arnold F.

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I have been purchasing some still lenses on eBay and it's been very problematic. Sellers explicitly say no haze or fog and when I ge the lens it's full of haze and fog. The method I use to examine the lens is to shine a small flashlight through it. I have been wondering, however, if this is an unrealistic and non-real-world test and if it is, therefore, unfair. When I hold the lens up to a bright window it looks real clean. Which test should I use? Window or flashlight?
 
A good test is to take some pictures with varying lighting situations - some with lights pointing at the lens and otherwise. If you don't see any undesirable artifacts you're probably good to go.
 
I could do that but wouldn't it be faster and more objective to just examine the lens itself? If it's foggy to the eye will that not affect the image?

That question brings up another I've had. Many ebay sellers list optical defects and then go on to say that it won't affect the image. I'm not sure I understand how fog or haze or scratches in a lens have no effect on the light passing through it? If they have no affect, why do we clean our lenses?
 
Ebay is a clearing ground for less than stellar copies of still glass.
 
In my experience, photo stores that have an ebay "presence" and have a 99% approval rating are generally pretty reliable (especially when they have over 1000 sales posted). I've gotten to know the ones I trust, and I've had few if any problems.

The sellers that are ordinarily lay people (ie not pros) often don't know what to look for, and send out lemons. Most of the problems I've had...seemed to have been because of inexperience, not malice. Returns have been ok and well dealt with in general, but I've learned to avoid these sellers when possible.
 
Louis, it's great to see that there is less effect on image than one might think.

My two questions remain:

- Is the flashlight test too stringent?

- and this is perhaps more rhetorical - if I explicitly ask a seller if there are cleaning marks, fog, haze, etc. and they explicitly say no, should I not expect to receive a lens with no cleaning marks, fog or haze? These people are sending me lenses with EXACTLY the problems I've asked them to rule out! The last problem lens was from a very articulate and experienced lens collector and sold in a thoughtful and well-presented auction; precisely the type of seller one looks for.

The reason I persist with the flashlight question is because, yes, I could mount the lens and shoot a bunch of stuff, but there's no way to know if I've shot covered every possible situation. I'd rather just examine the lens itself; that seems faster, easier and more accurate.
 
Arnold, I routinely test lenses - all lenses - by holding them up over a 60 or 75 watt lamp. Its fast, and its easy to see any defects both inside and on the outside of the front and rear elements. Similar to what you'd see with the flashlight test. It is not in any way too stringent a test! However, a film or digital shooting test of either a real world subject or a test chart, depending on one's goals for the lens, is the best way to know what a given lens can do.

I too, buy (and sell) on ebay and only very rarely run into problems. On the contrary I get amazing bargains on occasion.
 
Les Dittert said:
Ebay is a clearing ground for less than stellar copies of still glass.
Click to expand...

Absolutely not so.
Ebay is a clearing ground for everything.
I have bought and sold since '99 and only had a problem once with a lens. (light polishing scratches)
When I spoke to the buyer he discounted the lens by 50%.
The real trick is to look at the quality of the description, the photos and to not hesitate to ask questions.
People tend to tell the truth when confronted with specifics.
Unscrupulous sellers get dealt with by Paypal pretty easily (refund is quick until a dispute is resolved)
and curiously I have only had to resort to this with known commercial sellers vs private individuals.
 
I am talking about optical quality, not cosmetic issues. Mass market still glass are like snow flakes. Some are nice and sharp while others are not so good. So many photographers cycle through several copies before they find one they like. The others often end up on Ebay. They all might look the same, as in brand new.

Clayton Burkhart said:
Absolutely not so.
Ebay is a clearing ground for everything.
I have bought and sold since '99 and only had a problem once with a lens. (light polishing scratches)
When I spoke to the buyer he discounted the lens by 50%.
The real trick is to look at the quality of the description, the photos and to not hesitate to ask questions.
People tend to tell the truth when confronted with specifics.
Unscrupulous sellers get dealt with by Paypal pretty easily (refund is quick until a dispute is resolved)
and curiously I have only had to resort to this with known commercial sellers vs private individuals.
Click to expand...
 
Same experience here. I bought a whole collection of Minolta Rokkors (see my survival guide) and Zeiss Contax' from Ebay (Germany). Whenever there was a significant thing to complain about, sellers have not really been aware of it and offered to take the item back or offered significant discounts. I only ever sent one single lens back, in most other cases I went for the discount and had them serviced for that money by an excellent lens technician in my city.

I gathered really nice glass in the end, not a single lemon. Oh, BTW, as long as there is no fingerprint (acids in human sweat can damage the coating) I tend not to clean lenses too often. A bit of dust does less harm than too much cleaning.

Private sellers often found those lenses left by a deceased relative or neighbour and have no clue to shine a flashlight through them – many know nothing but point and shoot cameras. If you look back at their history it's easy to spot junk sellers.
 
Nope. Your methods are good. Use the torch. Lens techs at Duclos will do the same thing. In most cases they tell me it can be cleaned. I had some haze in my Super Speed set on the 85 I believe, didn't affect the picture in tests.

Arnold F. said:
I have been purchasing some still lenses on eBay and it's been very problematic. Sellers explicitly say no haze or fog and when I ge the lens it's full of haze and fog. The method I use to examine the lens is to shine a small flashlight through it. I have been wondering, however, if this is an unrealistic and non-real-world test and if it is, therefore, unfair. When I hold the lens up to a bright window it looks real clean. Which test should I use? Window or flashlight?
Click to expand...
 
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